Charge-air intercoolers are used, in a manner known in the art, to cool the air compressed by the turbocharger, or an air mixture composed of recirculated exhaust gas and fresh air. During the cooling of the air or the air mixture moisture, for example water from the air or the air mixture, may condense in the intake tract of the internal combustion engine, particularly in the charge-air intercooler. In order to prevent the liquid condensate escaping from the intake tract into the internal combustion engine and causing damage to the internal combustion engine and/or to sub-systems thereof, for example due to corrosion, the condensate must be removed from the intake tract.
Other attempts to address condensate formation in the charge-air intercoolers include collecting condensate, produced during cooling of the charge air, in a condensate reservoir and then draining this off. For example, this is shown by US 2010/0229549 A1, US2009/0031999 A1 and CN 201916043 U. Another possibility is to vaporize the condensate by supplying heat, that is to say by means of the hot charge air or the hot fresh air/exhaust gas mixture, so that the water vapor is fed to the internal combustion engine with the air/gas mixture, as described, for example, in WO2009/130083 A1 and DE 10 2006 050 806 A1.
EP 1 724 453 A1 also describes a thermal disposal of the condensate. Thermal disposal of the condensate is performed in three steps. A first step is to provide an exhaust-gas heated heat exchanger for heating the condensate. The second step is to provide a thermal reactor, which comprises a PTC heating element and which shuts off automatically when no condensate accumulates. A third step is to provide a further thermal reactor for residual heating, the vaporized condensate being electrically heated to 450° C., so that the nitric acid vapor is converted into its harmless constituents.
DE 10 2006 033 314 A1 describes a device and a method intended to avoid the formation of a condensate. Here, for example, any cooling of the surfaces of the heat exchanger below the limit is avoided by keeping its coolant temperature above the dew point of the medium to be cooled. This is to be achieved by reducing the quantity of coolant in the charge-air intercooler, for example, in extreme cases even reducing the coolant flow to ZERO, until the temperature of the coolant once again exceeds the lower temperature limit.
EP 2 418 370 A2 describes a method for regulating the temperature of the gas system of an internal combustion engine, recirculated exhaust gases and fresh air being compressed in a turbocharger. A first method for regulating the temperature of the charge air in the inlet manifold, a second method for regulating the exhaust gas recirculation rate and/or a third method for regulating the temperature of the recirculated exhaust gas as a function of the operating state of the internal combustion engine are performed in series and/or simultaneously.
EP 2 213 859 A2 is concerned with a method for regulating a charge-air intercooler, in which charge air mixed with the recirculated exhaust gas is cooled by leading it through the charge-air intercooler, the cooling capacity of the charge-air intercooler during operating of the internal combustion engine being adjusted as a function of two threshold values of the charge-air temperature of the charge-air intercooler.
Against this background this invention offers a solution for avoiding condensate formation despite recirculated exhaust gas being present and despite running the charge through a charge air cooler without the need for generating additional heat energy.
Further, increasing the dew point temperature at the charge-air intercooler may require generation of additional thermal energy. However, this may increase energy expenditures of the engine.
In one example, the issues described above may be addressed by a turbocharger arrangement comprising an internal combustion engine, a turbocharger for supercharging the internal combustion engine, and a charge-air intercooler located in an intake tract between the turbocharger and the internal combustion engine. The turbocharger arrangement further includes an auxiliary cooling system including a first feed line for supplying a first coolant to the charge-air intercooler, the first feed line positioned upstream of the charge-air intercooler and downstream of a cooling element, the first feed line including a heat recovery element. The heat recovery element may exchange heat between the first coolant and a heat transfer medium, the heat transfer medium including one of engine coolant or exhaust gas.
In one example, a second coolant from a main cooling system may be fed to the heat recovery element, a second feed line branching off from a bypass avoiding a main radiator and leading to the heat recovery element, a return line carrying the second coolant drawn from the bypass from the heat recovery element to a coolant pump. In this example, the heat recovery element is a coolant-coolant heat exchanger. As such, the first coolant may be heated by hotter engine coolant in the heat recovery element. In another example, exhaust gases of the internal combustion engine may be fed into the heat recovery element. In this example, the heat recovery element is a gas-coolant heat exchanger and hotter exhaust gases may heat the first coolant in the heat recovery element. In this way, the formation of a condensate in a charge-air intercooler can be reduced by increasing a temperature of the first coolant (e.g., the charge-air intercooler coolant), without the need to generate additional thermal energy.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.